The present application of configurational statistics to model nucleic acids or polynucleotides provides an essential first step in relating the subtle features of chemical architecture to the unique physical and biological properties of these macromolecules. Through a combination of semiempirical energy calculations and statistical mechanical analyses it is possible both to elucidate details of nucleic acid conformation and also to provide a rational understanding of observed experimental phenomena. A primary objective of these studies is to develope more realistic theoretical models of polynucleotides that include the effects of solvation and of long-range forces. A second aspect of these studies is to study the molecular basis of polynucleotide flexibility with special emphasis upon the molecular details of conformational transitions. The third goal of the program involves the analysis of nucleic acid conformation in various supramolecular complexes. These computations not only may supply useful information in predicting the secondary structure of polynucleotides but also may provide a molecular basis for understanding the remarkably accurate recognition of nucleic acid sequences by various site specific agents. Hopefully, the theoretical analyses of nucleic acid conformation, properties, and interactions may also anticipate problems of potential importance to experimental investigators.